CN114597436B - Protective coating for metal bipolar plate and preparation method thereof - Google Patents
Protective coating for metal bipolar plate and preparation method thereof Download PDFInfo
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- CN114597436B CN114597436B CN202210311073.7A CN202210311073A CN114597436B CN 114597436 B CN114597436 B CN 114597436B CN 202210311073 A CN202210311073 A CN 202210311073A CN 114597436 B CN114597436 B CN 114597436B
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Abstract
The invention belongs to the field of metal bipolar plates of fuel cells, and particularly relates to a protection device for a metal bipolar plateA coating and a preparation method thereof. The protective coating covers the surface of the metal bipolar plate substrate, the protective coating comprises a transition layer and an amorphous carbon layer, the amorphous carbon layer covers the transition layer, the transition layer is combined with the metal bipolar plate substrate, and the components of the transition layer comprise at least one of Ti and Cr. The design of the transition layer can improve the combination reliability of the protective coating on the surface of the metal bipolar plate, the amorphous carbon layer has good conductivity and corrosion resistance, the problem of poor conductivity caused by oxidation of the surface of the metal bipolar plate can be solved, and finally the average corrosion current density of the metal bipolar plate can be less than 0.03 mu A/cm 2 (kept for 24 hours under constant potential polarization of 0.6V), the interface contact resistance is less than 2mΩ cm 2 (1.4 MPa).
Description
Technical Field
The invention belongs to the field of metal bipolar plates of fuel cells, and particularly relates to a protective coating for a metal bipolar plate and a preparation method thereof.
Background
A fuel cell is an energy conversion device, which is regarded as one of the very potential clean energy sources, that converts chemical energy stored in fuel and oxidant directly into electric energy in an electrochemical reaction manner, isothermally. The battery using hydrogen or hydrogen-rich gas as fuel is hydrogen fuel battery, which has the advantages of high efficiency, environment protection, energy safety, simple structure, high reliability, good compatibility, etc.
Bipolar plates have been the key components of hydrogen fuel cells, and their materials, mass, volume, life and cost have been considered for major importance in industry development. Currently, graphite and metal are two common materials for bipolar plates. The graphite bipolar plate has the defects of high processing difficulty, crisp texture, large volume, high cost and the like, and has the problems of poor shock resistance, poor low-temperature starting and the like under the working condition of a vehicle, so that the application of the graphite bipolar plate in the aspect of a vehicle fuel cell stack is limited. The metal has excellent electrical conductivity, thermal conductivity, compactness and toughness, is easy to machine, can realize the preparation of an ultrathin bipolar plate, and can meet the requirement of a vehicle fuel cell stack on high volume ratio power. However, in the working environment of the proton exchange membrane fuel cell (such as low PH, high humidity and about 80 ℃ operating temperature), the metallic bipolar plate with low cost such as stainless steel, titanium and the like simultaneously has an oxidation medium and a reduction medium, and on the anode side, the metallic bipolar plate can slowly undergo electrochemical corrosion, multivalent cations generated by corrosion can diffuse into the proton exchange membrane, and the proton conductivity of the membrane is reduced; on the cathode side, the bipolar plate may undergo surface passivation in an oxygen-rich environment, resulting in an increase in surface contact resistance. Thus, the application of metallic bipolar plates solves two problems: firstly, the electrochemical corrosion problem under the acidic system of the proton exchange membrane fuel cell; secondly, passivation on the metal surface causes a problem of reduced conductivity. Aiming at the problems, the development of a protective coating with corrosion resistance and high conductivity and a preparation method thereof are very important, and are key to the application of the metal bipolar plate in a fuel cell.
Disclosure of Invention
The application provides a protective coating for a metal bipolar plate and a preparation method thereof, which are used for solving the technical problems of poor corrosion resistance and increased contact resistance in the application of the metal bipolar plate.
In a first aspect, the present application provides a protective coating for a metal bipolar plate, the protective coating covering a surface of a metal bipolar plate substrate; the protective coating comprises a transition layer and an amorphous carbon layer, wherein the amorphous carbon layer is covered on the transition layer, the transition layer is combined with the metal bipolar plate matrix, the components of the transition layer comprise at least one of Ti and Cr, and the amorphous carbon layer contains conductive carbon particle components.
Optionally, the thickness of the transition layer is 80-120 nm, and the thickness of the amorphous carbon layer is 70-800 nm.
Optionally, the transition layer is prepared by using a magnetron sputtering metal target, and the amorphous carbon layer is prepared by using an arc evaporation graphite target.
Optionally, the material of the metal bipolar plate comprises stainless steel or titanium.
In a second aspect, the present application provides a method for preparing the protective coating according to the first aspect, the method comprising the steps of:
placing a metal bipolar plate to be treated in a vacuum cavity, wherein an arc evaporation graphite target and a magnetron sputtering metal target are arranged in the vacuum cavity;
treating the metal bipolar plate to be treated with the magnetron sputtering metal target to obtain a first metal bipolar plate containing a transition layer, wherein the magnetron sputtering metal target comprises a Ti target or a Cr target;
and treating the first metal bipolar plate with the arc evaporation graphite target to obtain an amorphous carbon layer containing conductive carbon particles, wherein the amorphous carbon layer and the transition layer form the protective coating, and the protective coating covers the metal bipolar plate to be treated.
Optionally, before the metal bipolar plate to be treated is treated by the magnetron sputtering metal target, the method comprises: and heating the metal bipolar plate to be treated, wherein the target temperature of heating is 120-170 ℃.
Optionally, after the metal bipolar plate to be treated is heated, the method includes: performing plasma etching, and introducing argon, wherein the first flow rate of the argon is 100-200 sccm; and when the plasma etching is carried out, the bias voltage applied to the metal bipolar plate to be treated is-180V to-250V.
Optionally, when the metal bipolar plate to be treated is treated by the magnetron sputtering metal target, the pressure of the vacuum cavity is 3×10 -1 ～8×10 -1 pa, when the magnetron sputtering metal target is carried out, the bias voltage applied to the metal bipolar plate to be treated is-20 to-80V.
Optionally, when the first metal bipolar plate is treated by an arc evaporation graphite target, argon is introduced, and the arc evaporation graphite target current and bias voltage are set; the second flow of the argon is 250-400 sccm, the current of the arc evaporation graphite target is 90-110A, and when the arc evaporation graphite target is carried out, the bias voltage applied to the metal bipolar plate to be treated is-20 to-100V.
Optionally, the purity of the Ti target or the Cr target is > 99.7% and the purity of the graphite target is > 99.9%.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:
according to the method provided by the embodiment of the application, the protective coating covers the surface of the metal bipolar plate substrate, the protective coating comprises the transition layer and the amorphous carbon layer, the transition layer covers the surface of the metal bipolar plate substrate, the amorphous carbon layer covers the transition layer, the components of the transition layer comprise at least one of Ti and Cr, the bonding reliability of the protective coating on the surface of the metal bipolar plate is improved through the transition layer of Ti or Cr, the amorphous carbon layer contains conductive carbon particle components through the preparation process regulation and control, the contact resistance is obviously reduced, and the conductivity is improved. Meanwhile, the amorphous carbon layer has excellent chemical stability and strong acid corrosion resistance, can improve the corrosion resistance of the metal bipolar plate in the working process and avoid the condition of poor conductivity caused by oxidation, and finally can lead the average corrosion current density of the metal bipolar plate to be less than 0.03 mu A/cm 2 (constant potential polarization for 24 hours at 0.6V), interface contact resistance is less than 2mΩ cm 2 (1.4 MPa).
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a cross-sectional structure of a protective coating and conductive carbon particles inside an amorphous carbon layer in an embodiment of the present application;
FIG. 2 is a schematic view of conductive carbon particles on the surface of an amorphous carbon layer according to an embodiment of the present application;
fig. 3 is a schematic flow chart of a method for preparing a protective coating for a metal bipolar plate according to an embodiment of the present application;
FIG. 4 is a graph of interface contact resistance provided by examples and comparative examples of the present application;
FIG. 5 is a potentiodynamic polarization graph provided in examples and comparative examples of the present application;
FIG. 6 is a graph showing corrosion current density under 0.6V potentiostatic polarization provided in examples and comparative examples of the present application.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present application based on the embodiments herein.
Throughout the specification, unless specifically indicated otherwise, the terms used herein should be understood as meaning as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification will control. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the present invention. For example, room temperature may refer to a temperature in the range of 10 to 35 ℃.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or may be prepared by existing methods.
The technical scheme of the embodiment of the application aims to solve the technical problems, and the overall thought is as follows:
according to an exemplary embodiment of the present invention, there is provided a protective coating for a metal bipolar plate, the protective coating covering a surface of a metal bipolar plate substrate; the protective coating comprises a transition layer and an amorphous carbon layer, wherein the amorphous carbon layer is covered on the transition layer, the transition layer is combined with the metal bipolar plate matrix, the components of the transition layer comprise at least one of Ti and Cr, and the amorphous carbon layer contains conductive carbon particle components.
Specifically, the conductive carbon particles in the present application are generated on the surface of the amorphous carbon layer and are embedded and penetrated inside the amorphous carbon layer, which is more beneficial to the improvement of conductivity, and if the conductive carbon particles are generated on the surface only, the interface contact resistance is more than 5mΩ cm 2 The method comprises the steps of carrying out a first treatment on the surface of the In the present application, the conductive carbon particles make the interface contact resistance of the amorphous carbon layer reach 2mΩ·cm 2 The following is given. The amorphous carbon layer is of a diamond-like amorphous structure, has good chemical inertness and stability, and has excellent corrosion resistance compared with common metals; in addition, the conductive carbon particles embedded and penetrated in the amorphous carbon layer are not easy to oxidize, and the stability of good conductivity is maintained, so that the durability of the metal bipolar plate is enhanced.
By modifying the metal bipolar plate by adopting the protective coating, the Ti or Cr-containing transition layer improves the bonding reliability of the protective coating on the surface of the metal bipolar plate, and the amorphous carbon layer containing the conductive carbon particle component obviously reduces the contact resistance and improves the conductivity. Meanwhile, the amorphous carbon layer also has chemical stability and acid corrosion resistance, can improve the corrosion resistance of the metal bipolar plate in the working process, avoids the condition of poor conductivity caused by oxidation, and is beneficial to the improvement of the output power of the fuel cell. The protective coating is covered on the surface of the metal bipolar plate substrate, and the defects of micropores, looseness and the like are avoided through detection, so that the problems of corrosion resistance reduction, adhesive force deterioration, falling and the like can be effectively avoided. In addition, the preparation process of the protective coating is simple and feasible, is suitable for mass production, and has great practical value.
In some embodiments, the transition layer has a thickness of 80 to 120nm and the amorphous carbon layer has a thickness of 70 to 800nm.
The thickness of the transition layer is 80-120 nm, cr or Ti in the components belongs to strong carbon binding elements, can be diffused and injected to the subsurface of the metal substrate to form bonds under the action of high-energy ions, can form bonds with carbon atoms evaporated by an electric arc, has the positive effect of improving the binding force of an amorphous carbon layer and a metal bipolar plate, and avoids the adverse conditions of cracking and falling of a protective coating from the surface of the metal bipolar plate; the thickness of the transition layer and the amorphous carbon layer is controlled, so that the corrosion resistance and the conductivity of the protective coating on the surface of the metal bipolar plate can be further improved.
In some embodiments, the transition layer is prepared using a magnetron sputtering source and the amorphous carbon layer is prepared using an arc evaporated graphite target.
Specifically, the amorphous carbon layer is prepared by using an arc evaporation graphite target, the amorphous carbon layer has stable chemical property and good corrosion resistance, and conductive carbon particles are contained in the amorphous carbon layer and the surface of the amorphous carbon layer, so that the contact resistance can be obviously reduced, and the conductivity can be improved.
In some embodiments, the metallic bipolar plate comprises a material comprising stainless steel or titanium.
In particular, the metal bipolar plate includes, but is not limited to: 316L stainless steel foil or TA1 titanium foil with thickness of 0.1 mm.
According to an exemplary embodiment of the present invention, there is provided a method for preparing the protective coating, as shown in fig. 1, the method comprising the steps of:
s1, placing a metal bipolar plate to be treated in a vacuum cavity, wherein an arc evaporation graphite target and a magnetron sputtering metal target are arranged in the vacuum cavity;
s2, treating the metal bipolar plate to be treated by using a magnetron sputtering metal target to obtain a first metal bipolar plate containing a transition layer, wherein the magnetron sputtering metal target comprises a Ti target or a Cr target;
s3, treating the first metal bipolar plate by using an arc evaporation graphite target to obtain an amorphous carbon layer containing conductive carbon particles, wherein the amorphous carbon layer and the transition layer form the protective coating, and the protective coating covers the metal bipolar plate to be treated.
Specifically, the method comprises the following steps:
step one: respectively ultrasonically cleaning a metal bipolar plate in petroleum ether and alcohol solution for 10 minutes to remove surface pollutants;
step two: fixing clean metal bipolar plate on rotating frame and placing it in vacuum cavityThe chamber is heated and vacuumized until the temperature is 120-170 ℃ and the vacuum degree is less than 4 multiplied by 10 -3 pa conditions;
step three: starting a Hall ion source after introducing 100-200 sccm of high-purity argon, setting bias voltage to-180 to-250V, forming high-density ion flow to etch the surface of the substrate, and setting a rotating frame to rotate around a central shaft at a rotating speed of 1-3 rpm;
step four: the argon flow is regulated to 100-150 sccm, the bias voltage is regulated to minus 20-minus 80V, the target power is set to 2-5 kW, the magnetron cathode power is started, a Ti or Cr transition layer is formed on the surface of the substrate through magnetron sputtering of a high-purity metal target, and the pressure of a vacuum cavity is 3 multiplied by 10 during deposition -1 ～8×10 -1 pa, the time is 15-30 minutes;
step five: the argon flow is increased to 250-400 sccm, the bias voltage is set to-20 to-100V, an arc cathode power supply is started, the target current is 90-110A, and an amorphous carbon layer containing conductive carbon particle components is prepared on a transition layer by arc evaporation of a high-purity graphite target for 2-10 minutes.
In an embodiment of the present application, the placing the metal bipolar plate to be treated in the vacuum cavity includes: and carrying out ultrasonic cleaning pretreatment on the metal bipolar plate to be treated by using an organic solvent so as to remove oil stains and water stains on the surface of the metal bipolar plate to be treated. Any other treatment method can be adopted, for example, a hydrocarbon cleaning agent is adopted, so long as the purpose of removing greasy dirt and water stains on the surface of the metal bipolar plate is achieved.
In the embodiment of the application, the operation condition of the magnetron sputtering metal target is controlled, so that the microstructure of the transition layer is more compact and has better binding force with the metal bipolar plate substrate, and the performance of the transition layer for preventing the corrosive medium from rapidly penetrating into the metal substrate and binding the amorphous carbon layer and the metal substrate is improved.
In embodiments of the present application, the operating conditions of the arc evaporated graphite target include: the argon is high-purity argon, the flow is 250-400 sccm, the target current is 90-110A, the bias voltage is-20 to-100V, the deposition time is 2-10 minutes, and conductive carbon particles are arranged in and on the prepared amorphous carbon layer, so that the contact resistance can be obviously reduced, the conductivity can be improved, meanwhile, the chemical stability and acid corrosion resistance of the amorphous carbon layer can be improved, the corrosion resistance of the metal bipolar plate in the working process can be improved, and the deterioration of the conductivity caused by oxidation can be avoided.
In some embodiments, the method for treating a metallic bipolar plate to be treated prior to treating the metallic bipolar plate with the magnetron sputtering metallic target comprises: and heating the metal bipolar plate to be treated, wherein the target temperature of heating is 120-170 ℃.
In the whole, by heating to the target temperature, introducing 100-200 sccm of high-purity argon, setting a bias voltage of-180 to-250V, bombarding with plasma, removing residual stains and oxides on the surface of the metal bipolar plate to be treated, and etching a subsurface structure, so that the metal bipolar plate to be treated has good bonding force with the transition layer. The target temperature of heating is controlled to be 120-170 ℃, and the metal bipolar plate surface to be treated is activated without causing high-temperature annealing to reduce mechanical properties.
In some embodiments, after the heating of the metallic bipolar plate to be treated, the method comprises: introducing argon to perform plasma etching, wherein the first flow rate of the argon is 100-200 sccm; and when the plasma etching is carried out, the bias voltage applied to the metal bipolar plate to be treated is-180V to-250V.
In some embodiments, the pressure of the vacuum cavity is 3×10 when the metal bipolar plate to be treated is treated with the magnetron sputtering metal target -1 ～8×10 -1 pa, when the magnetron sputtering metal target is carried out, the bias voltage applied to the metal bipolar plate to be treated is-20 to-80V.
Specifically, the pressure was adjusted to 3×10 by introducing argon -1 ～8×10 -1 pa has the positive effects of stably generating glow and forming proper amount of argon ions to continuously sputter the high-purity metal target.
In some embodiments, the first metal bipolar plate is treated with an arc evaporated graphite target, argon is introduced and the arc evaporated graphite target current and bias voltage are set; the second flow of the argon is 250-400 sccm, the current of the arc evaporation graphite target is 90-110A, and when the arc evaporation graphite target is carried out, the bias voltage applied to the metal bipolar plate to be treated is-20 to-100V.
The reason for controlling the flow of the high-purity argon to be 250-400 sccm is that the arc is not easy to start when the graphite target is evaporated by the arc, and the working argon with larger flow has the positive effects of raising the pressure of the cavity, facilitating the gas discharge to start the arc and maintaining the stability of the arc discharge.
In some embodiments, the Ti target or the Cr target has a purity of > 99.7% and the graphite target has a purity of > 99.9%.
The reason for controlling the purity of the Ti target or the Cr target to be more than 99.7 percent is that the impurity elements in the metal target material are reduced, and the positive effect of improving the bonding force of the sputtering preparation transition layer is achieved; the reason for controlling the purity of the graphite target to be more than 99.9% is that the impurity elements in the graphite target material are reduced, and the active effect of improving the corrosion resistance of the prepared protective coating is achieved.
The method of the present invention will be described in detail with reference to examples, comparative examples and experimental data.
Example 1
The embodiment of the application provides a protective coating for a titanium foil bipolar plate, the protective coating covers the surface of a bipolar plate substrate, the protective coating comprises a transition layer and an amorphous carbon layer, the amorphous carbon layer covers the transition layer, the transition layer is combined with the bipolar plate substrate, and the composition of the transition layer is Ti. The thickness of the transition layer is about 120nm, the thickness of the amorphous carbon layer is about 200nm, and the amorphous carbon layer contains conductive carbon particle components.
The preparation method of the protective coating comprises the following steps:
s1, placing a titanium foil bipolar plate to be treated in a vacuum cavity, wherein an arc evaporation source and a magnetron sputtering metal target are arranged in the vacuum cavity;
s2, treating the 316L stainless steel bipolar plate to be treated by using a magnetron sputtering metal target to obtain a first metal bipolar plate containing a transition layer, wherein the magnetron sputtering metal target is a Ti target;
s3, treating the first metal bipolar plate by using an arc evaporation graphite target to obtain an amorphous carbon layer containing conductive carbon particles, wherein the amorphous carbon layer and the transition layer form the protective coating, and the protective coating covers the titanium foil bipolar plate to be treated.
The method specifically comprises the following steps:
step one: using a titanium foil bipolar plate with the thickness of 0.1mm as a substrate, performing ultrasonic treatment for 10min by using petroleum ether solution at room temperature to remove surface greasy dirt, performing ultrasonic treatment for 10min by using absolute ethyl alcohol to remove the surface greasy dirt and water stain, and wiping the surface greasy dirt and the water stain for later use;
step two: fixing clean titanium foil bipolar plate on a rotating frame, placing in a vacuum chamber, closing chamber door, opening heating device in the equipment to 150deg.C, and vacuumizing to 4X10 -3 pa or less;
step three: starting a Hall ion source after introducing 100sccm of high-purity argon, setting bias voltage to-200V, forming high-density ion flow, etching the surface of the substrate for 30min, and removing residual stains and oxides on the surface of the substrate to improve the interface binding force of a film deposited subsequently, wherein the rotating frame rotates around a central shaft at a rotating speed of 1-3 revolutions per minute;
step four: argon flow is regulated to 150sccm, bias voltage is reduced to-50V, target power is set to 3kW, a magnetron cathode power supply is started, a Ti transition layer is formed on the surface of a substrate through magnetron sputtering of a high-purity Ti target, and the pressure of a vacuum cavity is 4 multiplied by 10 during deposition -1 ～6×10 -1 pa, time 18 minutes;
step five: and (3) increasing the flow rate of argon to 300sccm, setting a bias voltage to-75V, starting an arc cathode power supply, setting the target current to 90A, and preparing an amorphous carbon layer containing conductive carbon particle components on the Ti transition layer by arc evaporation of the high-purity graphite target for 2.5 minutes to obtain the amorphous carbon layer with the thickness of about 240 nm.
Example 2
Example 2 differs from example 1 in that: when an arc evaporation high-purity graphite target is adopted on the Ti transition layer to prepare an amorphous carbon layer containing conductive carbon particle components, setting argon flow of 300sccm, setting bias voltage to-25V, starting an arc cathode power supply, setting target current to 90A, and setting the time to 2 minutes to obtain the amorphous carbon layer with the thickness of about 200 nm.
Example 3
Example 3 differs from example 2 in that: when an arc evaporation high-purity graphite target is adopted on the Ti transition layer to prepare an amorphous carbon layer containing conductive carbon particle components, setting argon flow of 300sccm, setting bias voltage to-50V, starting an arc cathode power supply, setting target current to 90A, and setting the time to 2 minutes to obtain the amorphous carbon layer with the thickness of about 220 nm.
Example 4
Example 4 differs from example 1, example 2 and example 3 in that: the metal bipolar plate to be treated adopts a 0.1mm 316L stainless steel foil, and a Cr transition layer is formed on the surface of the substrate by magnetic control sputtering of a high-purity Cr target.
Example 5
Example 5 differs from example 4 in that: and forming a Ti transition layer on the surface of the substrate by magnetic control sputtering of the high-purity Ti target.
Comparative example
A titanium foil substrate having a thickness of 0.1mm, on which no protective coating was prepared, was used as a comparative example.
Performance detection
The protective coatings of the metal bipolar plates obtained in the example groups and the comparative examples are tested by referring to the contact resistance test method and requirements in the GB/T20042.6-2011 proton exchange membrane fuel cell, and the contact resistances of the examples and the comparative examples are obtained as shown in figure 4. As can be seen from FIG. 4, the interface contact resistance of the surface-modified bipolar plate is significantly reduced compared with that of the uncoated bipolar plate, and the minimum value of the contact resistance can reach 1.125mΩ cm under the pressure of 1.4MPa 2 。
Protective coatings for metallic bipolar plates of the example group and comparative example were applied at 70 ℃ at ph=3h 2 SO 4 Electrokinetic polarization test (-0.4-1.2V) with oxygen gas introduced into corrosion solution of +0.1ppmHF vsAg/AgCl ) The polarization curve of the surface modified bipolar plate is shown in fig. 5. As can be seen from FIG. 5, the corrosion potential of the examples is higher than that of the comparative examples, showing that the protective coating in the examples has remarkable corrosion resistanceLifting at cathode potential (+0.6V) vsAg/AgCl ) The lowest corrosion current density can reach 0.1 mu A/cm 2 。
The protective coating of the example and the substrate of the comparative example were subjected to ph=3h at 70 ℃ 2 SO 4 In a +0.1ppmHF solution, oxygen was introduced for 24h potentiostatic (0.6V) vs.Ag/AgCl ) The polarization test results are shown in fig. 6. The corrosion resistance of the protective coating is obviously superior to that of a base material after long-time constant potential polarization in a PEMFC environment, which is consistent with the result of an electrokinetic potential polarization test, and the minimum corrosion current density is stabilized at 0.0034 mu A/cm 2 Compared with the comparative substrate, the corrosion current density of the substrate is reduced by two orders of magnitude, and the corrosion resistance is excellent.
It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (3)
1. The preparation method of the protective coating for the metal bipolar plate is characterized in that the protective coating covers the surface of the metal bipolar plate substrate; the protective coating comprises a transition layer and an amorphous carbon layer, wherein the amorphous carbon layer covers the transition layer, the transition layer is combined with a metal bipolar plate matrix, the components of the transition layer comprise at least one of Ti and Cr, the amorphous carbon layer contains conductive carbon particles, the conductive carbon particles are generated on the surface of the amorphous carbon layer and are embedded and penetrated into the amorphous carbon layer, the thickness of the transition layer is 80-120 nm, and the thickness of the amorphous carbon layer is 70-800 nm;
the method comprises the following steps:
placing a metal bipolar plate to be treated in a vacuum cavity, wherein an arc evaporation graphite target and a magnetron sputtering metal target are arranged in the vacuum cavity;
heating the metal bipolar plate to be treated, wherein the target temperature for heating is 120-170 ℃,
argon is introduced to carry out plasma etching; the first flow of the argon is 100-200 sccm; when the plasma etching is carried out, the bias voltage applied to the metal bipolar plate to be treated is-180V to-250V;
treating the metal bipolar plate to be treated with the magnetron sputtering metal target to obtain a first metal bipolar plate containing a transition layer, wherein the magnetron sputtering metal target comprises a Ti target or a Cr target;
treating the first metal bipolar plate with the arc evaporation graphite target to obtain an amorphous carbon layer containing conductive carbon particles;
when the metal bipolar plate to be treated is treated by the magnetron sputtering metal target, the pressure of the vacuum cavity is 3 multiplied by 10 -1 ~8×10 -1 pa, when the magnetron sputtering metal target is carried out, the bias voltage applied to the metal bipolar plate to be treated is-20 to-80V;
when the first metal bipolar plate is treated by an arc evaporation graphite target, argon is introduced, the current and bias voltage of the arc evaporation graphite target are set, the second flow of the argon is 250-400 sccm, the current of the arc evaporation graphite target is 90-110A, and when the arc evaporation graphite target is carried out, the bias voltage applied to the metal bipolar plate to be treated is-20 to-100V;
the metal bipolar plate is kept for 24 hours under constant potential polarization of 0.6V, and the average corrosion current density is less than 0.03 mu A/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the Interface contact resistance is less than 2m ohm cm under 1.4MPa 2 。
2. The method of claim 1, wherein the metallic bipolar plate is made of stainless steel or titanium.
3. The method of claim 1, wherein the Ti target or the Cr target has a purity of > 99.7% and the graphite target has a purity of > 99.9%.
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| CN113991134A (en) * | 2021-10-22 | 2022-01-28 | 北京格睿能源科技有限公司 | Amorphous carbon coating for fuel cell metal bipolar plate and preparation method thereof |
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| CN112582634A (en) * | 2020-11-18 | 2021-03-30 | 上海治臻新能源装备有限公司 | Multilayer composite carbon coating of high-corrosion-resistance fuel cell bipolar plate |
| CN113991134A (en) * | 2021-10-22 | 2022-01-28 | 北京格睿能源科技有限公司 | Amorphous carbon coating for fuel cell metal bipolar plate and preparation method thereof |
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